The Preparation Of Modified TiO₂ Photocatalyst And Study On Its Degradation To Norfloxacin

Antibiotics are widely used in fields of clinical medicine,animal breeding and aquaculture.As we know,only small part of the antibiotics are absorbed by organisms,it means that most of the antibiotics are discharged into the natural environment in the form of drug prototypes,then pollution comes in.In addition,a large number of antibiotic wastewater which is discharged form antibiotic production is becoming a huge challenge to environmental governance.If the problem of antibiotic pollution is not handled well,human health will be seriously threatened.Therefore,the study of antibiotic degradation has great signifificance.At present,TiO₂ photocatalytic oxidation technology is an important method with advantages of simple operation,green environmental protection,stable chemical property,innocuity,low cost to treat wastewater.However,pure TiO₂ is prone to recombination for photo-generated electron-hole pairs and has low utilization of solar light,which hinders its application potential.This paper mainly from the two aspects,the photocatalytic performance of TiO₂ was improved by modifying.1.In this paper,on the basis of the synthesis of anatase TiO₂ nanoparticles,the Pt modified TiO₂ was obtained by heat treatment with platinum chloride as the source.In the study of TiO₂ photocatalysis,it was found that there are a large number of surface states on the surface of TiO₂,these surface states increase the charge recombination and decrease the photocatalytic activity of TiO₂.The Schottky barrier can be formed on the-TiO₂ interface of the precious metal by using the precious metal modified TiO₂,which can effectively inhibit the recombination of electrons and holes and improve the photocatalytic properties of TiO₂.Firstly,TiO₂ nanoparticles were prepared by hydrothermal method,and the Pt modified TiO₂ was prepared by a simple method.With20 mg/L of norfloxacin as the target degradation,the results showed that the content of Pt was 0.76%,TiO₂（Pt-2）,and the degradation rate of norfloxacin was the best,which was about 95.44%,and the degradation rate was increased by 22% compared with that of pure TiO₂.In addition,we also studied the effect of TiO₂（Pt-2）dosage and the initial concentration of norfloxacin on the degradation rate.The results showed that 0.03 g was the best amount of catalyst TiO₂（Pt-2）.When the initial concentration of norfloxacin was5-20 mg/L,the degradation rate could reach more than 90%.It was linearly related totime t by ln（A/A0）,and the correlation coefficient R2 was greater than 0.96,which indicated that the reaction process followed the first order reaction kinetics.2.Without changing the anatase structure of TiO₂,using nitrate（magnesium nitrate,calcium nitrate,strontium nitrate）on TiO₂ surface modification.As the pure TiO₂photo-generated electron-hole pairs are prone to recombination,which is a key factor affecting the photocatalytic activity of TiO₂.Therefore,the reduction of charge recombination is the key to improve the photocatalytic activity of TiO₂.In this paper,Mg（NO₃）₂,Ca（NO₃）₂,and Sr（NO₃）₂ modified anatase TiO₂ were prepared and characterized by XRD and SEM.The photocatalytic activity of the modified TiO₂ was studied.Mg（NO₃）₂ modified TiO₂,the best molar ratio of Mg（NO₃）₂ and Ti O2 was 0.25%,the degradation rate of norfloxacin was 97.19%,compared with pure TiO₂,the degradation rate increased by 21%.When the initial concentration of norfloxacin was 5,10,15 and 20 mg/L,TiO₂（Mg-0.25%）on the degradation rate could reach more than95%.It was linear relationship with reaction time t by ln（A/A0）,and the correlation coefficient R2 was greater than 0.97,which indicated that the reaction process followed the first order reaction kinetics.Ca（NO₃）₂ and Sr（NO₃）₂ modified TiO₂ were similar to those of Mg（NO₃）₂ modified TiO₂ catalyst for degradation of norfloxacin.In the optimum molar ratio under the condition of active order nitrate modified TiO₂ photocatalytic degradation of norfloxacin was: TiO₂（Mg-0.25%）>TiO₂（Ca-0.25%）> TiO₂（Sr-0.25%）.3.Because TiO₂ is only absorbed by ultraviolet light and the utilization ratio of visible light is low,so it is not good to use sunlight.Therefore,broadening the photoreaction range of TiO₂ is one of the keys to improve the photocatalytic activity of TiO₂.In the paper,the nano TiO₂ was modified by the method of semiconductor composite.Since the band gap of Fe₂O₃ was narrow,2.2eV,it could absorb visible light.In the paper,TiO₂ nanoparticles was prepared by hydrothermal method.TiO₂/ Fe₂O₃ composite semiconductor was prepared by heat treatment,using ferric nitrate as iron source.With 20 mg/L norfloxacin for the degradation,and the photocatalytic reaction was carried out with xenon lamp after the adsorption equilibrium was achieved.The results showed that when Fe₂O₃ and TiO₂ weight ratio is 0.04,and the amount of catalyst is 0.05 g,the maximum of norfloxacin degradation,when the initial concentration of norfloxacin in 5-20 mg/L,the degradation rate was more than 85%.The correlation coefficient R2 was greater than 0.97,and the reaction process followed the first orderreaction kinetics.The reaction time t was plotted in a linear relationship with ln（A/A₀）.